Genetic counselling

10.4 Genetic counselling



Zornitza Stark, Martin Delatycki


Genetic counselling involves a health professional talking to an individual, a couple or a family about a medical condition or disease that is, or may be, genetic in origin. Genetic counselling is not always provided by genetic specialists (clinical geneticists or genetic counsellors). It is appropriate for paediatricians and disease-oriented specialists to counsel in their own area of expertise. It may be difficult, however, for the doctor who looks after a child with a genetic condition to challenge a family to look at their feelings in the genetic counselling context. Even when another practitioner provides genetic counselling to the immediate family, the genetic specialists will often be involved in counselling the broader family.


The provider of counselling for any particular condition or situation tends to evolve with time. As new technology arises it is often the genetic specialist who will counsel the family, but with time this often falls to the disease-oriented specialist and general practitioner. An example is counselling for advanced maternal age and tests to diagnose Down syndrome prenatally. In the 1980s medical geneticists and some specialized obstetricians largely undertook this. It is now usually done by obstetricians and general practitioners.



Genetic specialists


Clinical geneticists are medical practitioners who undertake specialist training in this discipline. Their primary training is usually in paediatrics or adult internal medicine but can be in other areas, such as obstetrics and gynaecology.


Genetic counsellors come from a range of different backgrounds, such as science, nursing and teaching. They undertake a basic training programme in both genetics and counselling, followed by on-the-job training.


Areas that are covered by genetic specialist practice include:



• dysmorphology


• prenatal counselling and testing


• neurogenetics


• cancer genetics


• bone dysplasias


• metabolic diseases.


As can be seen, it covers a wide age range of patients – from pre-conception to autopsy! Traditionally a paediatric specialty, the genetic specialist is increasingly involved in diagnosis and counselling for adult-onset diseases as more and more genes are discovered for these conditions.



Indications for formal genetic counselling


Anybody who suspects they might be at increased risk of a genetic condition or producing a child with a genetic condition or birth defect may wish to receive formal genetic counselling. This includes:



• individuals who themselves have a genetic disorder


• couples who have had a stillbirth


• couples who have had a child with a birth defect


• couples who have had a child with intellectual disability


• family history of any of the above


• family history of known genetic disorders, such as Huntington disease, muscular dystrophy


• multiple miscarriages


• exposure to radiation or drugs during pregnancy


• advanced maternal age


• consanguinity


• chromosome anomalies, including translocations and inversions


• cancers, particularly where there are multiple affected family members and/or where there is a very young age at disease onset.



Process of genetic counselling


Genetic counselling is the process by which individuals with or at risk of an inherited disorder are advised of:



• the consequences and nature of the disorder


• the probability of developing or transmitting the disorder, and


• the options open to them in management and family planning in order to prevent, avoid or ameliorate the disorder.


This is a complex process that encompasses both diagnostic and supportive aspects, and genetic specialists need to allow each family sufficient time in quiet surroundings for this to occur.


Diagnostic information is gathered by obtaining detailed histories or records of probands (the affected individual through whom a family with a genetic disorder is ascertained). Medical records and doctors’ reports are best obtained before undertaking counselling, as this makes the consultation more efficient. A pedigree is drawn with a minimum of three generations (see below). Probands and other members of the family are examined carefully and investigated as necessary. Only then can counselling be undertaken properly.


Genetic counselling is generally non-directive. A genetic specialist will not tell the family what they should do, but will help them reach an informed and reasoned decision based on the family’s own values. Thus, when a family asks, ‘Should we have another child?’, rather than giving a direct answer the geneticist might ask, ‘How would you feel about having another child with cystic fibrosis?’ In this way families are encouraged to explore their own feelings. For many families it is possible to be counselled in a single visit, but some families need to return for further discussions.


It is excellent practice to write to all families seen for counselling, restating the advice given to them at the time. This letter should be written in simple, clear language and outline the discussion that has taken place. A copy of this letter is sent to the family doctor and other specialists so that everybody involved has the same information. This document then serves as a valuable family record, can be shown to other professionals and overcomes the problem of selective recall.



Diagnostic precision


A critical element in genetic counselling is establishing the correct diagnosis. A precise diagnosis may not influence treatment but may dramatically alter the genetic counselling given to the patient and family. An example is muscular dystrophy. There are many different forms of muscular dystrophy. The principles of management are similar for these (e.g. appropriate splints, physiotherapy and occupational therapy). The risk for other family members, however, varies considerably depending on whether the muscular dystrophy is autosomal dominant, autosomal recessive, X-linked recessive or mitochondrial (see Chapter 10.2). To counsel a family appropriately, the exact diagnosis must be known.


A post-mortem examination may be necessary to establish a precise diagnosis. This can be of particular importance in a child with malformations or retardation, and in adults with neurological disorders. Post-mortem examinations need to be planned in advance, so that specific tissues can be obtained for biochemical study, electron microscopy or histochemistry. When death can be anticipated, it is best to raise the issue of an autopsy before death occurs. In practice this works better than asking permission immediately after the death, when families are grieving deeply. When permission for an autopsy has been granted, it is of the greatest importance that the parents return to discuss the autopsy findings fully.



image Clinical example


Thi and her partner Nam were planning to start a family. They sought genetic counselling because Thi’s sister had a son with muscular dystrophy. They were told that it is usually an X-linked condition, in which case there would be a significant risk that they could have a son with the same condition. After gaining permission from Thi’s sister, a muscle biopsy from the affected child revealed the diagnosis of limb-girdle muscular dystrophy 2B, an autosomal recessive condition. Thi and Nam were counselled that the risk for their own children was low.


Diagnostic precision may require the help of specialists who are expert in differentiating various neuromuscular diseases, retinal dystrophies and other complex problems. Dysmorphic and intellectually disabled children often require investigation before counselling can be given. An underlying chromosomal or metabolic basis should always be excluded and specific dysmorphic syndromes identified where possible (see Chapters 10.110.3 and 10.5).


With advances in DNA technology it has become essential to store samples of DNA from affected family members who are likely to die, as well as from relatives such as grandparents. This enables subsequent family members to benefit from advancing knowledge. Such samples can also be obtained, with permission, at the time of autopsy if not collected earlier. Appropriate samples to allow DNA to be stored include blood and fibroblasts from a small skin biopsy.



Obtaining and recording a family history


The family history is an essential part of genetic consultations, and is usually recorded graphically as a pedigree (family tree) using a standard set of symbols. The pedigree provides a concise record of both medical data and biological relationships between family members. It serves as a tool in making a diagnosis and establishing the pattern of inheritance. It can be used to identify relatives at risk of a genetic disorder, calculate their risks, and decide on the most



image Clinical example


George died from Hunter syndrome at 10 years of age in 1975. Hunter syndrome is a rare X-linked recessive neurodegenerative disorder. In 2010 his sister Eleni came for advice about her risk of having a son with Hunter syndrome. Fibroblasts from George had been stored. A gene mutation was found in DNA extracted from the fibroblasts, even though the gene had been cloned 15 years after George’s death. Eleni was shown not to carry the mutation. She could therefore be reassured that her risk of having a son with Hunter syndrome was no higher than that of any couple without a family history of the condition.

Related posts:

  1. Sudden unexpected death in infancy
  2. Birth defects, prenatal diagnosis and teratogens
  3. Neural tube defects, large heads and hydrocephalus
  4. The newborn infant: stabilization and examination

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Aug 4, 2016 | Posted by in PEDIATRICS | Comments Off on Genetic counselling

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